1. Field of the Invention
This invention relates to coil lifters and handling devices used for transporting coils of material such as steel, aluminum or the like. More specifically, this invention relates to coil lifters which protect the edges of the coil of material as the lifter arms are moved therealong. This invention can be incorporated into a coil lifter or assembled as an insert for mounting into each lifter arm of existing coil lifters and handling devices.
2. Description of the Prior Art
The coil lifters and handling devices used by many industries generally employ one of two lifting approaches. The approaches vary by the way in which a coil of material is positioned. Certain coils of material do not possess sufficient strength, especially soon after formation or rolling, to be laid on their edges. These coils are positioned, at rest, with the core through the center of the coil running horizontally.
The coil lifters used in transporting coils positioned in this manner typically employ the following approach. The coil lifter is suspended over the coil to be transported. The lifter arms of said coil lifter are moved apart a distance in excess of the overall coil width. The lifter arms are lowered about the coil of material until lifting surfaces at a lower end of each lifter arm are positioned for entry into the circular coil core ends. The lifter arms are moved together to close about the coil of material. Specifically, the lifter arms are effectively moved toward one another until the opposed front wall of each arm contacts with the edges of the coil therebetween. The lifter arms are then raised along the edges of the coil until the lifting surface of each arm contacts with upper curvature of each coil core end. Thereupon, the coil lifter and coil of material can be raised and moved about for transportation of the coil. Exemplary of such coil lifters are U.S. Pat. Nos. 3,002,779 and 3,771,666,
For those coil lifters presently known in the art, there is normally no resultant damage caused by the initial contact of the front wall of each lifter arm with the edges of the coil. However, the edges of the coil are damaged as the lifter arms are raised therealong for the contacting of the lifting surfaces with the upper curvatures of each coil core end. Further damage to the edges results when the coil is subsequently lowered after transporation.
Attempts have been made to modify the opposed front walls of the lifter arms of a coil lifter. For example, a face plate was secured to the front wall of each lifter arm in U.S. Pat. Nos. 2,120,639 and 3,001,812. Because these face plates were permanently secured to the front wall of each arm, they would likewise cause damage to the edges of a coil placed therebetween upon the raising of the lifter arms.
Unfortunately, the edges of a coil of material, especially soon after formation or rolling, do not possess sufficient rigidity to withstand the abrading movement of the lifter arms therealong. The forces exerted on the edges of a coil by said movement can bend or permanently wrinkle the coiled material. Most often, the damaged edges of a coil cannot be easily repaired. Instead, the damaged areas are typically removed after transporation of the coil to the desired area for subsequent use. Due to a general need for uniformity in coil size and due to the ease in cutting across and through all edges of a coil simultaneously, a substantial portion of each edge of a coil not damaged during transportation is also removed. Thus, the additional step of removing damaged edges is costly in terms of time, manpower and material wasted.
It is further known in the prior art to pad the arms of tongs which contact with fragile materials such as glass. U.S. Pat. No. 1,476,844. However, the addition of a padding material to the front wall of each lifter arm of known coil lifters would not minimize damage to the coil edges. The padding is still not responsive to the abrading movement of the arms along the edges of a coil.